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Complexity of Coupled Human and Natural Systems
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Integrated studies of coupled human and natural systems reveal new and complex patterns and processes not evident when studied by social or natural scientists separately. Synthesis of six case studies from around the world shows that couplings between human and natural systems vary across space, time, and organizational units. They also exhibit nonlinear dynamics with thresholds, reciprocal feedback loops, time lags, resilience, heterogeneity, and surprises. Furthermore, past couplings have legacy effects on present conditions and future possibilities.
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The Technology Path to Deep Greenhouse Gas Emissions Cuts by 2050: The Pivotal Role of Electricity
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Several states and countries have adopted targets for deep reductions in greenhouse gas emissions by 2050, but there has been little physically realistic modeling of the energy and economic transformations required. We analyzed the infrastructure and technology path required to meet California’s goal of an 80% reduction below 1990 levels, using detailed modeling of infrastructure stocks, resource constraints, and electricity system operability. We found that technically feasible levels of energy efficiency and decarbonized energy supply alone are not sufficient; widespread electrification of transportation and other sectors is required. Decarbonized electricity would become the dominant form of energy supply, posing challenges and opportunities for economic growth and climate policy. This transformation demands technologies that are not yet commercialized, as well as coordination of investment, technology development, and infrastructure deployment.
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Homo economicus Evolves
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Economic models can benefit from incorporating insights from psychology, but behavior in the lab might be a poor guide to real-world behavior.
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More Intense, More Frequent, and Longer Lasting Heat Waves in the 21st Century
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A global coupled climate model shows that there is a distinct geographic pattern to future changes in heat waves. Model results for areas of Europe and North America, associated with the severe heat waves in Chicago in 1995 and Paris in 2003, show that future heat waves in these areas will become more intense, more frequent, and longer lasting in the second half of the 21st century. Observations and the model show that present-day heat waves over Europe and North America coincide with a specific atmospheric circulation pattern that is intensified by ongoing increases in greenhouse gases, indicating that it will produce more severe heat waves in those regions in the future.
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From Death Comes Life: Recovery and Revolution in the Wake of Epidemic Outbreaks of Mountain Pine Beetle
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Excerpt : “Part of the initial increase in nutrients and moisture under dead and dying trees is due to reduced uptake,” Rhoades says. “But the sick and dead trees are also losing needles that fall to the ground and help retain soil moisture. And, as trees decay, they release nutrients back into the system.”
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Impacts Research Seen As Next Climate Frontier
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Scientists hope the next U.S. president will devote more of the billion-dollar
climate change research program to impacts
SCIENCE VOL 322
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Global Warming, Elevational Range Shifts, and Lowland Biotic Attrition in the Wet Tropics
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Many studies suggest that global warming is driving species ranges poleward and toward higher
elevations at temperate latitudes, but evidence for range shifts is scarce for the tropics, where the
shallow latitudinal temperature gradient makes upslope shifts more likely than poleward shifts.
Based on new data for plants and insects on an elevational transect in Costa Rica, we assess the
potential for lowland biotic attrition, range-shift gaps, and mountaintop extinctions under projected
warming. We conclude that tropical lowland biotas may face a level of net lowland biotic attrition
without parallel at higher latitudes (where range shifts may be compensated for by species from
lower latitudes) and that a high proportion of tropical species soon faces gaps between current
and projected elevational ranges.
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Impact of a Century of Climate Change on Small-Mammal Communities in Yosemite National Park, USA
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We provide a century-scale view of small-mammal responses to global warming, without
confounding effects of land-use change, by repeating Grinnell’s early–20th century survey across
a 3000-meter-elevation gradient that spans Yosemite National Park, California, USA. Using
occupancy modeling to control for variation in detectability, we show substantial (~500 meters on
average) upward changes in elevational limits for half of 28 species monitored, consistent with the
observed ~3°C increase in minimum temperatures. Formerly low-elevation species expanded their
ranges and high-elevation species contracted theirs, leading to changed community composition at
mid- and high elevations. Elevational replacement among congeners changed because species’
responses were idiosyncratic. Though some high-elevation species are threatened, protection
of elevation gradients allows other species to respond via migration
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Biodiversity Under Global Change
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Many common plant species, such as prairie grasses, have evolved traits for the efficient capture and use of two key resources that limit terrestrial productivity: nitrogen (N) and carbon dioxide (CO2). Over the past 60 years, human activity has vastly increased the availability of these resources. Atmospheric CO2 concentration has increased by 40%, and N availability has more than doubled. These changes are likely to have important consequences for species interactions, community structure, and ecosystem functioning. On
page 1399 of this issue, Reich investigates one important consequence, biodiversity loss, based on a long-term elevated CO2 and nitrogen fertilization experiment.
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Peatland Response to Global Change
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Peatlands can buffer the impact of external
perturbations, but can also rapidly shift to a
new ecosystem type, with large gains or losses
of stored carbon.
VOL 326 SCIENCE
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